Drying of yarns and the like



R. F. 'CQNAWAY ET AL,

DRYING OF YARNS AND THE LIKE 5' Sheets-Sheet 1 Files? Jan. 3, 1,947

INVENTORS FULLI/VFIMNCIS COR/AWAY 4g? IRA W'RGIL HITT ATTQRNEY FiledJan. 3, 194 7 R. F. GONAWAY ETAL,

DRYING OF YARNS AND THE LIKE mwmm 5 Sheets-Sheet 2 ZNVENTOREJWOLLINF'RQNGIE CONAWAY MTT jam W Rm w. @NAWAY AL fi fi DRYING 0F YARNSAND. THE LIKE 5 Sheets-Shem 5 Filed Jan. 5, 1,94?

INVENTOR. WOLLINFPANCIS CONAWAY mfin'm'z' IRA VIRGIL HIT'T I ATTORNEYgages r DRYING OF YARNS AND THE LIKE poration of Delaware ApplicationJanuary 3, 1947, Serial No. 720,030

8 Claims. (CL 34-41) This invention relates to the drying of yarns.threads, ribbons or filaments and more particularly to the provision ofimproved apparatus for the rapid drying of yarns, threads, ribbons orfilaments.

Previously. drying of yarns and the like has been eilected by passingthem through heated chambers, or over drying rollers, or by placingbobbins holding the wet yarn in heated chambers. These methods have notbeen incorporated in continuous spinning processes with completesuccess. Diiiiculties encountered have arisen from non-uniformity ofdrying, non-uniformity of shrinkage, or slow drying rates. Theseobstacles have led to yarn of inferior quality and have hinderedprocessing yarn and the like successfully at the high speeds essentialto an economically feasible commercial process. Another diillcultyfrequently encountered has been breakage and snagging of the wet yarnsdue to tension built up on the yarn during drying.

This invention has as an objective the provision of apparatus for therapid, uniform drying of yarns, threads, ribbons or filaments. A furtherobject has been the provision of a. drying process whereby yarns and thelike could be dried to a uniform moisture content at high speeds and atexceedingly high temperatures. A still further object has been therapid, uniform drying of yarns and the like under low tensionconditions, thereby minimizing yarn breakage. Other ob- Jects willappear hereinafter.

These objects are accomplished by the following invention, in which,broadly stated, individual ends of yarn and the like to be processed,are

rapidly dried as they are drawn at high speeds and under 'low tensionover curved, dryer plates heated at temperatures which are substantiallyabove the boiling point of water. The curvature of the dryer plates isadjusted to obtain maximum efllciency, the drying rate and yarn tensionsbeing so balanced to give optimum drying conditions. The yarns and thelike are guided over the dryer plates by means of yarn directing pins.These may be stationary or they can be either idling rollers or geardriven rollers. The guiding means may also include the use of groovesarranged arcuately in the surface of the, curved plates, the groovesbeing adapted to receive yarn or the like traveling across the plate.

In the drawings, in which like numerals reier to like parts, Figure 1represents an end view or a typical dryer plate 4, showing at l arectangular shaped groove and yarn 6 therein. Ordinarily these groovesare about of an inch wide and about /8 to A of an inch deep. However,the dimensions are not limited to these and the grooves may be larger orsmaller depending upon the size of the yarn or the like being processed.Generally, the grooves must be so designed to receive the yarn or thelike in such a way that there is sumcient clearance at the sides and topfor rapid evolution of moisture and steam. The dryer plates can bestacked in tier arrangement as is shown in Figure 2 or they may beplaced end-to-end (or straight way arrangement) as is shown in Figure 3,allowing for a straight pass of yarn. Further, a back-to-backarrangement as is shown in Figure 4, may be used. Instead of using aplurality of dryer plates a single long dryer plate, as is shown inFigure 5, may be employed. The plates used in any of these arrangementsare preferably bent on a radius from about 5 feet to about 32 feet. Theare of any plate used in these arrangements may be as much as or severalplates of smaller arc may be placed end to end to simulate a singleplate dryer of larger arc. In the tier arrangement, the yarn is passedover roller 2 which is preferably gear driven (not shown). In the otherarrangements, a stationary pin 3 is used in directing the yarn and thelike over the plates and through successive grooves if grooves areemployed. The pin may be replaced by an idling roller or a gear drivenroller.

The plates may be fixed and immovable or they may be so arranged tosimulate large diameter rotable drums moving at speeds substantiallydifierent than yarn speed and in the same or opposite direction of yarntravel. Figure 6 shows an end view of such a rotable drum 1, supportedand rotating on shaft 8 which is driven by an outsidepower source notshown. This drum may be cylindrical and continuous or it may besegmented, as shown by lines 9, each segment being supported on an arm(not shown) extending radially and in turn supported on shaft 8.Further, the segments may be arranged so that there are gaps betweensuccessive dryer plates. The plates may be smooth surfaced or they maycontain grooves, as shown by line It and in Figure '1.

yarn speeds and drum speeds which are substantially different.

The drying members employed in such a manner may be heated in wayssimilar to those employed for stationary plates, as is described below.The dryer plates are generally metallic and are heated electrically,numeral representing the heating element. However, the plates may becomposed of other materials such as glass or plastics, which may beappropriately jacketed and heated with usual media such as oil orsuperheated steam. High boiling organic liquids, such I exceedingly hightemperatures used, to employ as Dowtherm, and high melting inorganicsalt mixtures may also be employed as heating media. While Figure 1 hasshown only one groove per plate, the plates may be niulti-grooved,permitting the rapid drying of several yarns at one tim For rapid dryingthe radius upon which the plates are curved is critical. It has beenfound that a radius of about '7 feet produces the desired rapid drying.The curvature at this radius is correctly adjusted for most yarns.However, if the curvature is reduced, 1. e., a larger radius ofcurvature, greater drying times are needed to produce the same endcondition of the yarn under identical drying conditions. This is shownin Table I. The viscose type, regenerated cellulose yarn used had thefollowing characteristics: loll-denier, lo-filament and O-twist(100-40-0); 145 initial moisture; dryer travel was 144 inches.

TABLE I Eflect of curvature of dryer plates on drying 7' Radius 32'Radius 1135333? g g rffifih pee em pee emp, I. P. M. 0? gg .1. M. =0. ig

Thus, yarn containing 145% moisture could be dried to 10% moisture(calculated on a bone dry basis) at a speed of 10,000 inches per minuteon a plate bent on a radius of 7 feet, the plate temperature being 189C. At the same speed but at the higher temperature of 221 C. and on aplate constructed on a 32 foot radius, the same yarn could be dried toonly 16% residual mois- 'ture. At comparable temperatures, it wasnecessary to reduce the speed to 6,000 inches per minute to obtain yarnhaving 10% residual water. By reducing the curvature from a 7 footradius to a 32 foot radius the drying time required to produce the sameend yarn was almost doubled. Plates constructed on a radius of 5 feet oron a radius of 9 feet have been found to give satisfactory resultssimilar to those obtainedusing plates bent on a radius of '7 feet.

This invention is readily adaptable to bothlow denier yarns and the like(50 to 150 denier) and higher denier yarns (1100 to 2200 denier ormore), high speed. drying being accomplished with either type of yarn.While Table I and Table m refer to the drying of low denier yarn, TableIt gives examples of the drying of high denier-yarn. This yarn hadfinish applied to it. I A multi-plate dryer was used, the tierarrangement shown in Figure 2 being employed.

TABLE-.11

Drying of hightenacity 2200-denier, 960 fllament, viscose typeregenerated cellulose yarn at 6,000 I. P. M. to 11% water Per Cent PlateII Yarn Initial Temp., 48 Time Moisture "0.

In these examples, the total travel per pass was 75.4 inches. This totalrepresents a summation of the travel of the yarn on the plate, in airand around the rolls. As can be seen from a comparison of the above twosets of figures, the higher the initial moisture content of the yarn thehigher is the temperature required to d y yarn to; the same endcondition for a given drying time.

The effect of temperature distribution over the plates is apparentlynegligible. On several runs for 2200-denier yarn, the plate temperatureswere graduated to give temperatures as high as 371 C. on the first fewplates and as low as 177 C. on the last few. No significant differencecould be found in the drying rate for these runs and for other runs inwhich all the plates were maintained at a temperature equivalent to theaverage plate temperatures of the graduated series.

I The drying of low denier yarns was accomplished readily, Table 111indicating appropriate conditions. A multi-plate dryer of' the end-toendarrangement shown in Figure 3 was employed in these examples, the totalplate travel being 144 inches.

TABLE III Drying of low denier untwisted viscose type regeneratedcellulose yarns Denier and Initial Plate Speed Time Residual Hi0filament R10 per Temp count cent I. P. M. Secs. 0 Q (B. D. Basis) 150-60145 8. 000 l. 08 210 11.2 -40 10. 000 864 189 10. 0 75-30 145 10. (II)854 9. 0 75-30 145 13. 000 665 7. 7 50-20 145 13.)0 .665 135 10.3 100-40156 10. 000 864 175 6. 7 100-40 156 8,000 1.08 160 ll. 6

' three dryer plates laid end to end the tension build-up was asfollows:

TABLE IV Tension build-up for ZOO-denier yarn Y 1-1. 5 Less than 1.0

Thus, the' apparatus and process of this invention permit the drying ofyarns under relatively low tensions, being generally in the range of0.01 to 0.5 gram per denier.

The plates used in the examples given in Table it were constructed onthe basis of a 7 foot radius. Reduction of the curvature of the platesto a radius of 32 feet resulted in a decrease in the tension build-up,the tension build-up in each example of Table IV being then less than 1gram. However, the drying time needed to drythe yarn and the like to anacceptable residual moisture content was materially increased.

If wet yarn or the like is drawn over. cold dryer plates, an extremelylarge tension build-up results. This tension exceeds the breakingtension of the wet yarn and probably is due to the surface tension ofthe water in the yarn. As pointed out above this efiect disappears whenthe yarn is drawn over hot dryer plates. It is postulated that theyarnactually rides on a blanket of steam. Intimate contact with the surfacesof the plates, whether grooved or not, is avoided. The temperaturesrequired to obtain satisfactory drying rates frequently are above thesoftening points or charring points of the material of which the variousyarns are composed. Plate temperatures may be varied from 100 C. to 500C. Higher or lower temperatures may be employed depending upon themoisture content of the yarn, speed of yarn thread, position of theplate in the drying cycle and composition of the yarn. Temperatures inthe range of 115 C. to d50 C. are preferred for most operations. Caremust be taken to avoid charring and burning. In this connection, theyarn speeds must be adjusted so that burning is avoided. Speeds of yarnwhich have been used successfully have been as low as 800 and as high as26,000 inches per minute. Higher or lower speeds might be employed,however, if desired; Yarn speeds and plate temperatures are adjusted foreach yarn dried to avoid scorching, melting or burning of the yarn. ifthe residual moisture content of the yarn is reduced too much, charringmay occur. The combined features of this invention, namely the curve ofthe plate, the guiding means and the use of low tensions allow for thedrying of yarn and the like with minimum contact with hot stationarysurfaces. Hence, the yarn may be dried rapidly yet under very lowtensions and with infrequent snagging and breakage of the yarn.

While it is not essential to use grooved plates, it is frequentlyadvantageous to do so. The grooves may be of any shape, thoserectangular or U-shaped being generally preferred. The depth of thegroove does not appear to be critical. The use of grooved drying platesresults in a drying apparatus which is easier to string-up and whichinvolves a minimum of entanglement of the separate threads being dried.The grooves function as additional guiding means and further force theyarn into very intimate contact with the heat radiating from the sidesof the groove. v

upon the area of the yarn exposed as the yarn passes over the heatedplate. A flattening or spreading out of the filaments in each yarnpermits faster heating and more rapid drying. This spreading out may beaccomplished, for'example, by passing the yarn over a crowned roller atsuch points as 2 or 3 in the drawings. Convergence of the filaments intoa single thread after drying may be done readily by means of a groovedroller, for example.

In general no adverse effects on the physical properties of the yarnprocessed on the dryer plates of this invention at the exceedingly hightemperatures occur. This is true in all instances in which the finalmoisture content is in the range of 5% to 15%. If this content isreduced to below 3.5% or 4%, danger of degradation becomes appreciable.But even yarns drastically dried to 3.5% to 4% moisture show littlereduction in quality. For example, when 2200-denier yarns were dried tomoisture contents to about 3.5% to 4.0% regain, only one physicalproperty, oven-dry cord tenacity, was affected. Oven-dry cord tenacitiesare obtained by drying the sample substantially to bone dryness and thentesting rapidly prior to appreciable moisture regain. The oven-dry cordtenacities of yarns dried this drastically by the process of thisinvention were on the average only 0.1 gram per denier lower thansimilar tenacitles measured on control yarns. All other properties wereunaifected. When textile yarns, that is, yarns of low denier, were driedby the process of this invention to 6% to 7% residual moisture, nodegradation at all occurred.

Another outstanding advantage of the dryer of this invention is theuniformity of shrinkage that yarns demonstrate that the process of thisinvention is superior in respect to other methods,

such as drying on a bobbin. Examplesof shrinkages obtained upon dryingIOU-denier yarn on 3 plates equivalent to 144'. inches of travel aregiven I in Table V below.

TABLE V Shrinkage of -4047 viscose type regenerated cellulose yarn g ggTension Shrinkages I. P. M Grams Per cent 13. 000 3. 0 5.05:0.5 10 0002. 25 4.5i035 8. 000 1-1. 5 4.0:l;(..25 6, 000 Less than 1.0 3.8=l=0.1

difliculties are encountered. When unfinished viscose rayon yarns,containing 80% water, were dried at 6,000 I. P. M., residual carbondisulflde flashed and burned with a blue flame in the first 24 to 36inches of travel. However, no visible bad effects were noted and thephysical properties, 1

such as tensile strength and elongation were unaffected.

While the invention has been described in reference to viscose typeregenerated cellulose yarns, it is understood that the apparatus andprocess of this invention are applicable to other yarns and the like,whether composed of synthetic or natural occurring materials. Thus,yarns and the like composed of cellulose derivatives, such as celluloseacetate, cellulose acetate-propionate, ethyl cellulose, etc., polyestersand polyamides. polyacrylonitrile, other polyvinyl compounds, proteins,etc. may be processed efllciently in the apparatus described herein.

As a further example, 450 denier "Acele yarn was dried fromapproximately 100% moisture to essentially bone dryness at a dryertemperature of 186 C., the dryer travel being 49 inches and the yarnspeed being 816 inches per minute. The dryer plates used in thisparticular experiment contained grooves which were 1; of an inch wideand of an inch deep, the grooves being spaced on /z of an inch center to1 inch centers. Since the apparatus and process of this invention aregenerally applicable, the examples 'which have been given areaccordingly illustrative only and are not to be considered aslimitative.

Any departure from the above description which conforms to the presentinvention is intended to be included within the scope of the claims.

We claim:

1. Yarn treating apparatus comprising members having arcuated surfacesbent on a radius between about 5 feet and about'32 feet; means fordirecting yarn over the said surfaces under a. tension between about0.01 and about 0.5 gram per denier; means for avoiding direct contact ofsaid yarn with said surfaces; means for heating said surfaces.

2. Yarn treating apparatus comprising members having arcuated surfacesbent on a radius between about 5 feet and about 32 feet; means fordirecting yarn over the said surfaces under a tension between about 0.01and about 0.5 gram per denier, said members being in an end-to-endarrangement; means for avoiding direct contact of said yarn with saidsurfaces; means for heating said surfaces.

3. Yarn treating apparatus comprising members having arcuated surfacesbent on a radius between about 5 feet and about 32 feet; means fordirecting yarn and the like over the said surfaces under a tensionbetween about 0.01 and about 0.5 gram per denier, said members being in2. tier arrangement; means for avoiding direct contact of said yarn withsaid surfaces; means for heating said surfaces.

- 4. Yarn treating apparatus comprising members having surfaces curvedon a radius between about 5 feet and about 32 feet; means for directingyarn over said surfaces, the said means including grooves arrangedarcuately in the said surfaces; means for avoiding direct contact ofsaid yarn with said surfaces; means for heating said surfaces.

5. A process for treating yarn which comprises passing the yarn overmembers having surfaces curved on a radius between about 5 feet andabout 32 feet, the said surfaces being heated at temperatures between C.and 450 C. and the said yarn being passed over the said surfaces in amanner whereby direct contact of said yarn with said surfaces is avoidedand at a rate of speed suflicient to prevent scorching.

6. A process for treating regenerated cellulosic yarn which comprisesheating members having surfaces curved on a radius between about 5 feetand about 32 feet at temperatures between 115 C. and 450 C.; passing thesaid yarn over the said surfaces under a tension of about 0.01 to about0.5 gram per denier in a manner whereby direct contact of said yarn withsaid surfaces is avoided and at a speed of at least 800 inches perminute.

7. A process for treating yarn which comprises passing the yarn overmembers having surfaces curved on a radius between about 5 feet andabout 32 feet, the said surfaces being heated at temperatures between115 C. and 450 C.; avoiding direct contact of said yarn with saidmembers; and rotating the said members at a speed substantiallydifferent than the speed of the said yarn.

8. A process for treating yarn which-comprises passing yarn-over membershaving surfaces containing grooves and curved on a radius between about5 feet and about 12 feet, the said surfaces being heated at temperaturesbetween 115 C. and 450 C. and the said yarn being passed arcuatelythrough said grooves in a manner whereby direct contact of said yarnwith said surfaces is avoided and at a. rate of speed sufilcient toprevent scorching.

ROLLIN FRANCIS CONAWAY. IRA VIRGIL HITT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

